Performance assessment of a R290 air-to-water heat pump for the HVAC system retrofit in an academic building through numerical simulation validated with monitored data
Propane is expected to be the most widespread refrigerant in the next generation of heat pumps due to its very low GWP value and optimal thermo-physical properties, which guarantee a wide operational range. In this paper, a new reversible Air-to-Water Heat Pump (AWHP) utilizing R290 as the refrigerant and having a rated heating capacity of approximately 60 kW is presented. The main features of the AWHP are discussed in detail, emphasizing the technical characteristics of the heat pump components and the unit performance as a function of the operating conditions. In order to assess the effective performance of the AWHP on a seasonal basis, an academic building located in Forlì (North of Italy) was considered. The HVAC system was based on condensing gas boilers and a conventional air-to-water chiller. The building was renewed during the spring of 2024 by installing two units of the AWHP mentioned before. Each unit is equipped with a datalogger, which enables the real-time monitoring of the HVAC system and heat pumps performance (i.e., heating/cooling capacity, absorbed power input, inlet/outlet water temperature). In this work, numerical models of the building, coupled to both the baseline and the retrofitted HVAC system, were developed. First, the building energy model was calibrated with thermal and electrical energy bills collected every month. Then, the potentially achievable energy savings by adopting the propane heat pumps were assessed through numerical simulations. The results show that the non-renewable primary energy demand of the HVAC system can be reduced strongly, up to 60%, with the refurbished system. Results also indicate that the heat pump performance is significantly influenced by the terminal unit typology.